1. Field of the Invention
This invention relates to exterior building wall systems utilizing wall panels in horizontal application. The wall panels are fastened to spaced apart vertical mullions which are secured to the exterior building perimeter frames. The wall surface is formed by multiple wall panels joined together along their side edges to form the horizontal joints and spaced apart between the panel ends at the panel end supporting mullion locations to form the vertical joints of the wall system. This type of panel arrangement is known as horizontal application of wall panels. This invention relates to the methods of sealing the vertical joint to prevent water leakage in the horizontally applied exterior wall panel systems.
2. Description of the Prior Art
Any wall panels having water repellent end closures are useful in a horizontal wall panel system. To seal the panel joints including horizontal and vertical joints, the use of caulking, gasket, or the combination thereof is well known in the art. It is also well known that perfect air tight seal is difficult if not impossible to achieve no matter what type of sealant is used due to the variations of workmanship and relative joint movement induced by thermal and wind loads.
Therefore, to provide a water tight exterior wall system, other provisions must be added to the sealing system. The following three methods of sealing the panel joints are known in the art.
Method 1 is to seal the joints behind the exterior wall surface within the panel depth and to provide an internal drainage system incorporating internal horizontal gutters at each level of horizontal joints. Since internal darinage system is provided, the wall system will achieve water tight performance if the joints in the internal gutters are maintained in good condition. However, the addition of the internal gutter system is expensive and thus, the system is normally used in the high priced wall system. PA0 Method 2 is to seal the joints at the exterior surface of the wall with curable caulking and to provide an internal drainage system which is simpler and less costly than Method 1 to drain the water out at intermittent levels or at the wall base. This method is normally used in the medium priced wall system. The water tight performance of this system is usually good also. PA0 Method 3 is to seal the horizontal joint within the panel depth and to seal the vertical joint to the mullion and to cover the vertical joint with a joint cover for appearance purpose. This method is most economical and is usually used in the low priced wall sysstem. However, since there is no internal drainage system in this method, numerous failures of water tight performance have been reported for jobs utilizing this method due to water leakage through the vertical panel joints. PA0 Principle 1: Pin holes in any sealant line will be developed due to workmanship and joint movements induced by thermal load or wind load. PA0 Principle 2: Due to the surface tension of water drop, vertically running water along a small gap joint will not penetrate through the small gap if the air pressure on both sides of the gap is equalized to a degree that the pressure differential is incapable to overcome the surface tension of the water drop. PA0 Principle 3: Pin holes in a sealing line will produce water leakage when water runs over the pin hole areas and the sealing line is subjected to a pressure differential greater than the surface tension of the water drop. PA0 Principle 4: Pin holes in a sealing line will not produce water leakage if no water runs over the pin hole areas even if the sealing line is subjected to a pressure differential greater than the surface tension of the water drop. PA0 Principle 5: Vertically running water along the corner of a vertical groove tends to stay in that corner due to the increased contact surface at the corner.
Typical application of this method are seen in the construction utilizing composite foam panels or honeycomb panels.